This paper examines the application of TiO2-mediated heterogeneous photocatalysis for the degradation of a mixture of fiber reactive dyes in a simulated dyebath effluent. The dyehouse effluent was treated in a supported thin-film-fixed-bed reactor by using commercial TIO2, two products with a pure anatase crystal phase and one with an anatase (70%)-rutile (30%) hybrid structure. The experimental results have demonstrated that the anatase-rutile modification markedly outperformed the treatment efficiency of the anatase TIO2, specially in terms of dearomatization kinetics. Complete decolorization was achieved by the selected photocatalysts, whereas the chemical oxygen demand (COD) and total organic carbon (TOC) content of the simulated reactive dyebath effluent could only be removed at a relatively low degree by the 100% anatase powders during the investigated reaction period. The collector area requirements per order of color removal (CAO) ranged between 10-12 m(2)/(m(3) x order).